Background: The development of targeted anti-cancer therapies requires the demonstration of the effects of the investigation agents on the intended target and pathway and the discovery of the markers that can be associated with the response. Thus, we are engaged in detecting the effects of agents on pathway-specific biomarkers and in discovering response biomarkers to be implemented in correlative studies. I. Technology, Assay Design, Development, and Validation. We develop, validate, and implement assays for clinical specimens using electrochemiluminescence (ECL)-based immunoassays. This is the most sensitive and quantitative immunoassay technology platform today. The ECL platform is well suited for this ongoing task because it offers a high degree of flexibility, stability and reliability. It is capable of multiplex analysis to determine the levels of total and phospho-proteins in a single assay well using a limited amount of clinical specimens. Because clinical samples may vary dramatically, the ability to normalize these samples beyond total protein concentration is critical in generating statistically significant data with patient specimens. At the present, we developed, validated and utilized a range of biomarker assays to address the following areas in clinical investigations: 1. Angiogenic factors in plasma and up-regulation of HIF1a in hypoxic tissues for Anti-angegenic agents 2. Cytokines and growth factors for varies targeted agents 3. Cell surface receptors changes as a results of the administration of targeted therapeutic antibodies 4. Intracellular phosphoproteins for a varies kinase inhibitors 5. Apoptotic biomarkers for targeted and cytotoxic agents II. Current and Recently Completed Biomarker Studies. Currently, we are engaged with 10 clinical protocols at NCI-CCR. For many of these clinical trials, we helped to design, develop, validate, and implement customized biomarker assays for correlative analytical studies. The following are some examples: 1) For a phase II clinical trial of sorafenib in androgen-independent prostate cancer (PI, William Dahut), our laboratory performed assay validation with the investigational agent sorafenib and implemented assays with bone marrow biopsy specimens to determine its effects on the targeted MAP kinase pathway (Dahut WL, et al. Clin. Cancer Res. 14: 209-14, 2008). 2) For another clinical trial that investigated a combination targeted therapy against ovarian cancer (PI, Elise Kohn), our group developed assays and performed the analysis of angiogenic factor vascular endothelial growth factor (VEGF) and cytokines, including interleukin-6 (IL6) and interleukin-8 (IL8) from plasma obtained from the patients throughout the drug trial period (Azad NS, et al. J. Clin. Oncol. 26: 3709-14, 2008). 3) In another rapamycin trial (PI, Chand Khanna), we measured the changes in the relative changes of S6RP signaling from both osteosarcoma biopsies and peripheral blood mononuclear cells (PBMC) following the administration of rapamycin. Our data showed a highly statistically significant reduction of p-S6RP in PBMC. The p/t-S6RP ratio changed from 25% pre-drug to 0.5% post-drug with p less than 0.001, with samples obtained from day 2 to the end of the study. Our results further showed that there is a high degree of variation in tumor biopsies. The statistically significant effect of rapamycin on the S6RP pathway can only be demonstrated as p/t-S6RP ratio using our duplex assay capable of quantitatively measuring both p-S6RP and t-S6RP in the same assay well (Paoloni MC et al., PLoS One, 5:e11013, 2010).